Control device for once-through vapor generators



Aug. 22, 1944;

F. RIEDEL CONTROL DEVICE FOR ONCE-THROUGH. VAPOR GENERATORS Filed Aug 27, 1940 ,Ihven-ton FERDINAND 215051. 7

By I afll-lo'r'ney.

Patented Aug. 22, 1944 CONTROL DEVICE FOR ONCE- THROUGH VAPOR GENERATORS Ferdinand Riedel, Berlin- Mariendorf, Germany; vested in the Alien Property Custodian Application August 27, 1940, Serial No. 354,449

In Germany June 3, 1939 3 Claims. 122448) This invention relates to vapor generators of the forced passage type, and more particularly to means for controlling the operation of such vapor generators.

Vapor generators of the forced passage type comprise a once-through vapor passage which re- 5 the generator load and therefore being adapted ceives liquid at one end and delivers superheated to be used as a load impu s f controlling the vapor at the other end. supply control valve 4. A bellows I is acted. upon In a generator of the forced passage type-in by the pressure in the conduit 6 for controlling distinction from any other generator type--the 10 a lever B S y mounted t 9 and provided evaporation zone is liable to be displaced due to W th a counterweight l0. Up n a l increase any change in the generator load, it being imthe weight I0 rocks the lever B in clockwise manderstood that a decrease results in a displacement er so that e jet p pe I Of a W no s en of the'evaporation zone in the direction toward J'et pipe'relay deflects to the left thereby increasthe superheater section or the output end of the w ns the pre u b low he pist n f a s rvopassage, whereby the length 'of the superheater motor I2 operatively connected to the valve 4. section will be changed and the temperature of cc rd y the Valve 4 Will be further Op the consumption vapor varied accordingly. and the flow of the supply and the quantity of 'For this reason a previous proposal h b feed water are correspondingly increased in remade to provide means for preventing the evapsponse to the increase of the generator load. A oration zone from undergoing any displacement 1 restriction I3 in the conduit 2 is provided to crein the passage. ate a differential pressure of a feed water quan- The present invention is based on the percepy impulse acting 1 a phr M for e tion that the uncontrolled displacement of the r ne a st ri a ti n th jet p p II y evaporation zone is adapted to be used for cona s a W known counter-lever and a trolling the operation of the generator by digplacratio slide IS. The increase of the feed water ing the evaporation zone at will in aecordance flow due to the p o t e valve 4 sults n with the operating condition of the generator, an i e e in pressure on t e left s de of t more particularly in accordance with the generdiaphra m M whi h l ads to an in s n the ator load. counter-force restoring the jet pipe I I to its mid- 'Such' a positive displacement of the zone of dle or neutral position-shown in Fig. 1. evaporation may be advantageous both in the The Water pplied by the conduit 2 to the p sen'se'of a displacement toward th output sage I is preheated inthe first section thereof and toward the input end of the passage upon a and evaporates in the second section. In the load increase. The former would be desirable if range of the e p at n ne a p ssu i itis essential to maintain the temperature of the pu e o it I8 branches off and leads to a delivered superheated vapor constant whilst the S 9 for controllin a Valve 20 in the main latter would be preferable to enhance the storing Consumption Conduit this Valve be arcapacity of the generator. ranged beyond the point of communication 2! In order to more fully explain the subject'mat.. 40 of the pressure conduit 6 above referred to. The ter of the invention and its aims and objects refbellows I9 controls a j p 22 y means of a erence is had to the accompanying drawing i lever system similar tothat shown and described Which inconnection with the bellows "I. The jet pipe Fig. l is a diagrammatic view of a vapor gen- 22 controls a servo-motor 23, the piston of which erator of the forced passage type provided with is operatively connected to the valve 20 and cona controlling device according to my invention, trols this valve in such a manner that the presand sure in the passage at H, i. e. the evaporation Figs. 2 and 3 are diagrammatic views showing pressure, remains substantially constant. Assuma reversing device as more fully explained below. ing that, due to the load increase, the pressure The p r generator in the usual manner comat IT decreases, then the jet pipe 22 will deflect prises a once-through fluid passage I communicating at the input end with a supply conduit 2 supplied by means of a pump 3 and provided with a controlling valve 4 for varying the supply in response to the generator load. To the output end'of the passage I is connected a main or consumption conduit 5 leading to a consumption apparatus (not shown). A pressure impulse conduit 6 branches off from this conduit 5, the'pressure in said impulse conduit varying as a function of to the left and the piston of the servo-motor 23 will move downwardly thereby further closing the valve 20, so that the pressure at I! is again increased until the predetermined pressure value to be maintained constant is obtained. This pre-v determined pressure value is represented by a counter-spring 24 acting on the jet pipe 22. Any variation in the initial tension of the spring results in a corresponding variation in the pressure at I! in the passage.

In the embodiment shown means are provided for likewise controlling the fuel supply in response to the generator. An electric motor 25 is coupled with a'conveyor 26of a well known pulverizer system and with a measuring fan 21 producing, in a conduit 28, a pressure varying in response to the fuel feed. For controlling 'the fuel feed the motor 25 will be controlled by means of a rheostat 29 inserted in the motor circuit (not shown). 4

in the motor circuit a servo-motor 30 is provided controlled by means of a jet pipe relay 3| together with a bellows 32 acted upon by the pressure in a pressure impulse conduit 33 communicating with the main or consumption conduit as at 34, i. e; beyond the valve 20. Upon a load in crease the pressure in the conduit 33 decreases so that the jet pipe 3| deflects to the left and displaces the piston of the servo-motor 30 to theright, thereby decreasing the resistance of the rheostat 29 and increasing the speed of the motor '25; Accordingly the pressure in the conduit 28 increases sothat the pressure on the left side of the diaphragm 35 increases and exerts a restoring action on the jet pipe. 3| similar to the diaphragm I4 acting on the jet pipe I I'.

Beyond the point H in the passage a temperature sensitive -member 36 is provided for 1 controlling, by means of a relay 31 '(the details of which are more fully explained below), a servo motor 38, the piston of which is connected to a'cam' 39 for displacing the well known ratio slide '40, .by means of which the transmission ratio between 32 and 35 may be variedin a manner .well known to anyone familiar with the Askania' jet. pipe relay. The influence exertedv .15 For varying the part of the rheostat inserted Now by maintaining the pressure at IT con stant in the manner described above and by likewise maintaining constant a higher temperature at 36 the evaporation zone is prevented from undergoing any displacement in the passage for the following reason: If, for instance, the evaporation zone is displaced in direction toward the output end, the temperature at 36 will decrease due'to the shortening of the superheating path up to 36. Thereforethe servo-motor 38 increases the fuel supply :to the generator by means of theslide valve 40 until the temperature at 38 again risesto its predetermined value, which is the case as soon as the evaporation zone returns to H.

Asstated above, the initial tension of the spring 24 acting. upon the jetpipe 22 represents the value. of the pressure to be maintained constant at |1.' Accordingly the pressure at H may be adjusted by var'ying the tension of the spring 24. In accordance with the present invention means are provided for varying the tension of the spring 24 so as to displace at will the evaporation zone in response to any operating condition of the generator. In the embodiment shown, the tension of the spring 24 is varied in accordance with the generator load. To this end a bellows 4| is acted upon by the control pressure in the conduit 33, a branch conduit 42 leading from 33 to 4|. A jet pipe 43 actuated by the bellows 4| controls a servo-motor 44, the piston of which carries a cam 45, upon which the spring 24 reacts.

This arrangement operates as follows: At a load increase, the impulse pressure in 33, 42 and 4| is reduced, consequently the jet pipe 43 is defiected to the left and the piston of the servomotor 44 and the cam 45 forced upwardly. Thus the spring 24 is expanded and, provided that a constant pressure exists at H, i. e. on the bellows IS, the jet pipe 22 is deflected to the left. The valve 20 is closed still further, which results in an increase of pressure at H until the equilibrium is re-established between the reduced tension of the spring 24 and the force acting on the jet pipe 22 in the opposite direction, i. e. the force resulting from the difference between the bellows I9 and the weight l9a.

A pressure increase at H, such as results from an increase in load and temporary closing movement of valve 2|], causes a displacement of the evaporation zone toward the output end of the passage 1|, as a higher pressure is coordinate with a corresponding higher saturated vapor temperature which only occurs at a point lying a distance between the points I! and 36 in accordance with th pressure'increase at this point.

In this way the length of the superheater section is reduced. This reduction in length does notrepresent a drawback, onthe contrary, at ;a

load' increase the rate of the flow of vapor through the superheater section increases correspondingly. This rate increase, however, results in an enhancement of the'heating process with the .consequence that the temperature of the issuing superheated vapor would increase if the length of the superheating section, i. e. the position of the evaporation zone in the passage, were:

to remain thesame. The reduction in length of the; superheater section results in a compensation in the sense of maintaining constant the temperature of the issuing superheated vapor.

A load decrease and consequent opening movement of valve 2|! by the control mechanism results inan increase in tension of the spring 24,

i. e. 'a pressure decrease at IT, and hence in a displacement toward the input end of the passage of the evaporation zone, which of course likewise acts in the sense of maintaining constant the temperature of the superheated vapor entering the main or consumption conduit 5.

If it is'desirable that a load increase be accompanied by adisplacement of the evaporation zone toward the input end, it will only be necessary to exchange the action of the conduits 46,

41 leading'from the jet pipe 43 to the servo-motor H, i. e. the tension of thespring 2' 1.

ceivi'ng nozzle of the jet pipe 43 is connected to the lower point of connection of the servo-motor 44 and the right-receiving noz'Zle'to the upper point of connection. The arrangement according to the invention thus operates in the sense of the temperature of 'the issuing vapor 'being maintained constant.

If the two cocks are turned 90 simultaneously, the result is the position shown in Fig. 3 in whichthe left receiving nozzleof the jet pipe l3'com municates with the upper end of the servo-motor 44 and the right nozzle with the lower-end of. same. At the same deflecting direction of the jet pipe 43 the controlling direction is thus. reversed (which is tantamount to increased storing capacity of the vapor generator).

As will be readily understood, 'the novel and useful displacement of the evaporation zone can be obtained not only by adjusting th'e tension of the spring 24, i. e. the value-of the pressure at ll, but also by adjusting the valueof the temperature at 36 to be maintained constant. In like marmer it may be arranged for the pressure value at IT and the temperature value at 36 to be adjusted in response for instance to the load variation.

The means above described are based on the principle to displace the evaporation zone by varying the pressure to be maintained constant at It is, however, likewise possible to displace the evaporation zone by varying the temperature value to be maintained constant, i. e. the temperature at the member 36. To this end the relay 31 must be influenced in the same manner as the relay 22 by varying the initial tension of the spring 24.

The relay 3'! comprises a jet pipe 50 the receiving nozzles of which communicate with two conduits 5!, 52 leading to the servo-motor 38 for controlling, by means of the cam 39, the ratio slide 46. 'The temperature sensitive member 36 is shown to be a tube 53 connected to a loop la of the passage i, so that the tube 53 assumes the temperature of the loop l a, i. e. the temperature of the vapor. The tube 53 is of a material having a high coefficient of heat expansion. Within the tube there is provided a rod 54 one end of which is fastened to one end of the tube 53 whilst its other end is connected to a lever 55 swingably supported on a knife edge 53 and cooperating with the jet pipe 53. In the opposite direction a spring 5! acts upon the jet pipe as is usual in the well known Askania jet pipe relay.

The knife edge 56 may be displaced in a direction transverse to the lever 55 by means of a link 58 swingably mounted at 59 and operatively connected to the rod 63 of a servo-motor piston 6!. This servo-motor belongs to the jet pipe 43, two conduits 43a, Ala branching on the conduits 43, 4! as shown in Fig. 1.

The conduits 46 and M as well as the conduits 46a and .1a are each provided with a stop valve 62, 63 and 64, 65, respectively in such manner that by closing the valves 64, 65 the evaporation zone will be displaced by varying the initial tension of the spring 24 whilst by closing the valves 32, 63 the evaporation zone will be displaced by varying the temperature value to be maintained constant at 36 in the manner now to be described.

Be it assumed that the evaporation zone shifts. due to an abnormally low load or to the temporary checking action of valve 26 due to a sudden increase in load, in the direction toward the output end of the passage 1. Such a displacement results in a decrease of the temperature at 36 so that, due to a contraction of the tube 53, the lever 55 rocksclockwise thereby deflecting the jet pipe 50 likewise in a'clockwise direction and displaces the piston of the servo-motor 38 to the left. In consequence thereof the fuel supply will bed'ecreased until the evaporation zone returns toll"! as described above. The same operation may be obtained by varying the temperature value to be maintained constant in thefollowing manner: As soon as the knife edge 53 is displacedto the right, for instance, the spring 51 deflects the jet'pipe in counterclockwise manner, thereby increasing the. fuel. supply and thuszincreasing the-temperature to be maintained constant at 36. As willibe reach ily understood from-the drawing, any displacement of the servo-motor piston 6| results-ma displacementof the knife edge 56 corresponding to the variation in the tensionof the spring 24 produced by a deflection of thejet pipe. 43, which results from any load variation.

If it should be desirable to vary'not only :the

pressure value to be'maintained constant at ll or the temperature value at 36, but both of. said values, all the valves 62, 33', 63 and 35'would be opened. In such event I prefer to provide means for a successive operation'of the servo-motors M and 6! in such a manner that upon a load variation the servo-motor 44' is first put into operation which influences the spring, i. e. the pressure to be maintained constantat I1 and subsequently the servo-motor 6 I, which influences thetempep ature to be maintained constant at 36. In view of this springs and 61 may be arranged at both sides of the servo-motor piston 6| to retain the piston in its middle position until the servo-motor 44 approaches the end of its stroke.

In another embodiment the springs 66 and 61 may be inserted in the servo-motor 44 so that the servo-motor 6| is put into operation before the I servo-motor 44.

For the sake of completeness it may be submitted that it is further possible touse, instead of the springs 66 and 61, any other arrangement according to which the servo -motor, which should operate first automatically controls the valves 62, 63 and 64, 65 of the other servo-motor. The respective valves remain closed until the piston of the servo-motor operating in the first place approaches the end of its stroke. The servomotor operates by the automatic opening of said valves.

It is to be noted that the desired displacement of the zone of evaporation need not be efl'ected in dependence on the load but may just as well be achieved in response to other operating values as for instance the temperature of the issuing superheated vapor. Control in response to the temperature of superheated vapor would be desirable particularly where the zone of evaporation is to be displaced as a means of preventing fluctuations in the superheated vapor temperature.

The invention is not restricted to the particular embodiment shown and described by way of example only. This embodiment may be modified in a plurality of ways-without departing from the spirit of my invention as defined in the appended claims.

What is claimed is:

1, In a device for controlling a vapor generator of the forced passage type having a oncethrough fluid passage receiving liquid at one end and delivering superheated vapor at the other end, comprising, in combination, pressure controlling means for maintaining a constant pressure in said passage at a point determining the position of the zone of evaporation, temperature controlling means for maintaining a constant temperature in said passage at a point predetermined in relation to said constant pressure point, the temperature to be maintained constant corresponding to the distance from and the position of said constant temperature point in relation to said constant pressure point, means for adjusting the temperature value to be maintained constant, and means for actuating said adjusting means in response to the operating condition of the generator to displace at will the zone of evaporation.

2. In a device for controlling a vapor generator of the forced passage type having a oncethrough fluid passage receiving liquid at one end and delivering superheated vapor at the other end, comprising, in combination, pressure controlling means for maintaining a constant pressure in said passage at a point determining the position of the zone of evaporation, temperature controlling means for maintaining a constant temperature in said passage at a point predetermined in relation to said constant pressure point, the temperature to be-maintained constant corresponding'to the distance from and the position of said constant temperature point in relation to said constant pressure point, means for adjusting the pressure value to be maintained constant, means for adjusting the temperature Ill value to be maintained constant, and means re,--x sponsive to the generator load connected to actuate successively said pressure adjusting means and said temperature adjusting means.

3. In a device for controlling a vapor generator of the forced passage type having a oncethrough fluid passage receiving liquid at one end, anddelivering superheated vapor at the-other end, comprising, in combination, pressure controlling means for maintaining a constant pressure in said passage at a point determining theposition of the zone of evaporation, temperature controlling means for maintaining a constant temperature in said passage at a point predetermined in relation to said constant pressure point, the temperature to be maintained constant cor--. responding to the distance from and the position of said constant temperature point in relation to said constant pressure point, means for adjusting the ratio of the constant pressure value and the constant temperature value, means responsive to the generator load connected to actuate said adjusting means for displacing the zone of evaporation in accordance with the generator load variations, and additional means for reversing the adjusting means so that, upon a load increase, the zone of evaporation will be automatically displaced toward the input end and toward the output end of said passage alternately.

FERDINAND RIEDEL. 

